1. Field of the Invention
This invention relates to a blood bag system, and more particularly, to a blood bag system capable of transfusing a necessary component (e.g. plasma) and returning the remaining component (e.g. corpuscle or cell) of blood to the donor.
2. Description of Prior Art
Prior art blood bag systems will be discussed with reference to the drawings.
Referring to FIG. 1, there is diagrammatically illustrated a typical blood bag system according to the prior art. The blood bag system 1 comprises first and second blood bags 2A and 2B each having an inlet 3 for collecting blood, an outlet 4 for transfusing a plasma component, and another outlet 5 for transfusing a cell or corpuscle component of blood, and containing a given volume of an anticoagulant previously injected therein. First and second sections of tubing 6A and 6B are connected at one end to the inlets 3 of the blood bags 2A and 2B, and at the other end collectively to one end of a main section of tubing 8 via a branch pipe 7. A hypodermic needle 9 for collecting blood is connected to the other end of the main section of tubing 8. Cell return means 11 is connected to one of the collecting sections of tubing, 6B in the illustrated embodiment, via a branch pipe 10.
To carry out plasma transfusion, the blood bag system 1 may be operated as follows. The needle 9 is inserted into the donor's vein and blood is collected in the first blood bag 2A. Thereafter the first blood bag 2A is disconnected from the first section of tubing 6A, and placed in a centrifuge to separate the blood into plasma and cell components. The thus separated plasma component is transfused from the bag 2A to the patient through the plasma outlet 4 while the separated cell component is returned or transfused back from the bag 2A to the donor through the cell outlet 5, return means 11, and needle 9. The procedures of blood collection, separation, transfusion, and return are repeated for the second blood bag 2B. With this blood bag system, a necessary amount of plasma can be collected by repeating the procedures of blood collection, transfusion and return without unnecessarily increasing the volume of blood taken out of the donor in each collecting process. Furthermore, the need for inserting the puncture needle into the donor's vein for every blood collecting process is eliminated to minimize the damage to the vascular wall and the pain to the donor by puncture.
In the above-illustrated blood bag system 1, for the purpose of preventing the anticoagulant in each of the blood bags 2A and 2B from being transferred to the other blood bag during autoclave sterilization as well as for the purpose of ensuring that the blood collected in each of the blood bags 2A and 2B be kept anticoagulant, the blood collecting inlet 3 of one of the blood bags, for example, blood bag 2B is removably fitted with a spherical bead 12 to block the flow path of the inlet 3.
However, in the manufacture of the blood bag system 1, the step of mounting the bead 12 at the blood collecting inlet 3 of the second blood bag 2B is complicated and troublesome. When blood is to be collected in the second blood bag 2B, the bead 12 must be removed from the inlet 3 and dropped into the bag 2B. Not only the step of removal of the bead 12 is cumbersome, but the periphery of the inlet 3 might be damaged or fractured by the nail or the like. Moreover, during the centrifugal separation after blood collection, the bead 12 in the second blood bag 2B might be centrifugally forced against the inner wall of the bag with possible fracture. When the bead 12 is mounted only at the inlet 3 of the second blood bag 2B, the anticoagulant contained in the first blood bag 2A will flow into all the flow paths of the sections of tubing 6A and 6B and the main section of tubing 8 to wet the tube inner surface By this reason, the volume of anticoagulant contained in the first blood bag 2A must be somewhat larger than that in the second blood bag 2B, further complicating the manufacture process. In addition, since the flow paths to be wetted by the anticoagulant contained in the first blood bag 2A total to a considerable length, it becomes difficult to previously distribute the anticoagulant properly throughout the flow paths because of flow resistance and other factors.
FIG. 2 diagrammatically illustrates another prior art blood bag system as disclosed in Nevens et al., U.S. Pat. No. 4,407,660. This blood bag system 13 is similar to the blood bag system 1, but different from the previous system in that it uses a plug 14 capable of blocking and allowing communication through both the connection between the second section of tubing 6B and the main section of tubing 8 and the connection between the cell return means 11 and the main section of tubing 8.
In this blood bag system, when the plug 14 blocks communication through the connection between the second section of tubing 6B and the main section of tubing 8, the anticoagulant contained in the first blood bag 2A wets the first section of tubing 6A and the main section of tubing 8 and the anticoagulant in the second blood bag 2B wets the second section of tubing 6B. It is thus possible to substantially equalize the volumes of anticoagulant contained in the blood bags 2A and 2B and to cause the anticoagulant to be properly or uniformly distributed throughout the flow paths because the flow paths to be wetted are individually assigned to the respective anticoagulant fractions in the bags.
The above-described blood bag system, however, requires careful operation of withdrawing the plug 14 halfway to communicate the second section of tubing 6B with the main section of tubing 8 when blood is to be collected in the second blood bag 2B. Care must be taken so as not to fully remove the plug 14 from the cell return means 11. Further, when the cell transfusion outlet 5 of each of the blood bags 2A and 2B is connected to the cell return means 11, the plug 14 must be fully withdrawn from the cell return portion 11, with the possible entry of bacteria from the atmosphere into the main section of tubing 8.